Another way to do it is to agree on things that you will continue to pay for (like school-related expenses, uniforms, etc, basic food and her cost of attending family outings like the movies or a dinner) and what you won't, which would be all the rest - stupidly expensive jeans, outings with friends, I-Pods, mobile phone bills (I HATE kids having them BTW - I am a lawyer coped without one until 2 years ago LOL!). $85 won't go far.....